this is a workaround for the endian problem in BG/Q, see issue 206
added a safety measure for definition of _POSIX_C_SOURCE
fixed correlator normalisation with respect to changed inversion call in operator struct
Merge pull request #209 from urbach/FixOnlineNormalisation

fixed correlator normalisation with respect to changed inversion call in...
moved time.h inclusion below the POSIX def
Merge pull request #208 from urbach/fixPOSIXbug

this is a workaround for the endian problem in BG/Q, see issue 206